Over the years, the most commonly used techniques for both identity verification and the identification of potential crime suspects have been the use of fingerprints and photographs or “mug shots”.
Originally, fingerprinting was done by inking a suspect's finger and applying the inked finger to paper. As can be readily understood, fingerprint information in this form was difficult to use. Making a fingerprint match was an extremely time-consuming task. Digital technology significantly advanced the art of fingerprinting. Inked images could be scanned, the image digitized and recorded in a manner that could later be searched in a reasonably expeditious manner by computer. Problems arose, however, due to the quality of inked images. Over- and under-inking resulted in blurred or vague images, thus rendering the digitized information useless. Further, the process of scanning an inked image was relatively time-consuming.
These and other problems led to “live scanning”. According to live scanning techniques, the fingerprint of a suspect is scanned directly from the suspect's finger, as opposed to being scanned from an inked image of the print. More specifically, live scans are those procedures that capture fingerprint ridge detail in a manner which allows for the immediate processing of the fingerprint image with a computer. Original work in the field dates back to original patents filed in 1964 concerning techniques used to capture high contrast images of fingerprints for photographic or digital captures of fingerprints.
Since their introduction, live scans have become an important tool for law enforcement. The live scan has the potential to overcome inherent weaknesses in the ink capture of fingerprints and provide immediate transmission of fingerprint images; and allow for image enhancement if necessary.
These characteristics provide law enforcement with the ability to improve the quality of the fingerprint database, thereby improving the likelihood that identifications may be made either from latent fingerprints or from identity verification checks. In addition, live scan fingerprints are easily adaptable to computerized storage and processing techniques, increasing cooperation and fingerprint data transfer between various police agencies.
Systems, which optically, or optically and mechanically, generate fingerprint images have been in use for quite some time. Several such fingerprinting systems are disclosed in Fishbine et al., U.S. Pat. Nos. 4,811,414 and 4,933,976; Ruell German Patent No. 3423886 A1; Becker U.S. Pat. No. 3,482,498; McMahon U.S. Pat. No. 3,975,711; Schiller U.S. Pat. Nos. 4,544,267 and 4,322,163; Marcus U.S. Pat. No. 4,533,837 and White U.S. Pat. No. 3,200,704. However, the problem with all of these systems is that they are only capable of providing optical or optical and mechanical fingerprint images at a central location such as the police station.
U.S. Pat. No. 5,122,152 to Fishbine et al. solved this problem by providing a portable and lightweight fingerprint scanning system which can optically generate fingerprint images. This system is ideal for traffic officers and other law enforcement professionals who want to perform immediate identity and background checks on individuals while in the field. The system described in Fishbine et al, U.S. Pat. No. 5,122,152, uses the optical principle of total internal reflection. When a finger is positioned on a finger-receiving surface, an optical image of the ridge and valley pattern on the surface of the finger (i.e., the fingerprint) is propagated from the finger-receiving surface.
The finger-receiving surface is a prism with illumination provided on side surfaces by an illumination source that consists of light-emitting diodes attached to the side surfaces of the prism. The bottom surface of the prism is coated with an opaque material such as black paint. The prism is designed to utilize the optical principle of frustration of total internal reflection as described in Fishbine et al. U.S. Pat. No. 4,811,414. These properties result in a visual fingerprint image of a finger placed on the finger-receiving surface with “light” areas corresponding to ridges of the fingerprint and “dark” areas corresponding to valleys of the fingerprint. The image is captured using a video camera and the data is digitized for display, storage, and transmission. Optical fingerprint sensors, as described in the reference patent, require complex optical path corrections. Video cameras, prisms, lenses, and mirrors used in the system must be precisely located.
An investigator at an incident scene is often at risk due to lack of information. If a suspect or witness feels the investigator will obtain information that will incriminate them, the risk to the investigator is increased. In these situations, investigator safety is increased if the portable device for capturing images may be operated using a single hand. Although mobile, the system described in Fishbine et al, U.S. Pat. No. 5,222,152, does not allow for single handed operation. Single handed operation means the ability to hold the device in one hand and use the same hand to control the device while conducting an investigation. The portable system described in Fishbine et al, U.S. Pat. No. 5,222,152, required the officer to use both hands, holding the device in one hand while using the other hand to capture images or enter text. In capturing images, the operator holds the device in one hand and is required to align the suspect's finger in the correct position to capture a usable print. There is a need for a system that allows for single hand operation and image gathering. This would provide a law enforcement officer with additional safety by having one hand free to protect oneself from potential harm that may be inflicted by a suspect.
The orientation and location of a captured fingerprint significantly impacts the quality of the response received from the search system. It is important to align the finger along the capture surface properly, capture the core of the print, and prevent movement by the witness or suspect as the print is being captured. It is desirable for the system to orient and align the finger without requiring the officer to use both hands.
Any optical fingerprint system is susceptible to intense ambient lighting. Intense ambient light which strikes the fingerprint receiving surface produces bright images on the video camera which captures the fingerprint image. If the ambient light intensity is equivalent to the light source of the fingerprint capture system, the bright spots will interfere with the fingerprint image being captured. Thus, when the finger-receiving surface on the system disclosed in Fishbine et al, U.S. Pat. No. 5,222,152, was exposed directly to ambient lighting, the operator was required to reorient the device to eliminate interference from the bright ambient lighting. During an investigation, these extra actions are undesirable.